1. Field of the Invention
This invention relates to a method of manufacturing disposable, breathable receptacles for storing articles in sterile condition.
2. Description of the Prior Art
Currently, receptacles for sterile packaging of articles, and primarily those used for medical applications, fall principally within three general categories: pouches with one side made of polyethylene-coated paper or of polyethylene film and the other side consisting of a breathable material such as paper or "Tyvek" (a spun polyolefin of the du Pont Company); pouches or bags having an all-paper construction utilizing adhesive bonds with the entire surface area of the receptacle serving as the breathing membrane; and pouches or bags with walls made substantially entirely of a material, typically polyethylene or polypropylene, which is impermeable to both microorganisms and sterilizing vapor and having a breathable strip or patch covering a slit or port in the wall.
Receptacles in current use often have limited shelf lives due to deterioration of the membrane material as a result of changes in ambient temperature and humidity which cause flexing, distortion and sometimes pinholding of the membrane material. This is particularly true of receptacles whose breathing membrane constitutes a large portion of the overall area of the receptacle such as those in which the membrane forms an entire wall, or both walls, of the receptacle. Stresses applied to the membrane walls of such receptacles can be transferred to a vulnerable spot accelerating the formation of pinholes or otherwise weakening the structure sufficiently to eventually create a break through which microorganisms can enter. Another disadvantage of such receptacles is that the stored article is directly exposed to large areas of the fibrous membrane with the possibility of dislodging fibers through abrasion or other physical contact.
Moreover, receptacles that are fabricated of two materials are expensive. The breathable membrane, if paper, must be surgical grade and is significantly more expensive than ordinary paper while "Tyvek" is several times the price of paper membrane material. Some such receptacles have small windows or ports covered by a patch of vapor-permeable material. The manufacture of such receptacles requires exact registration between the port, patch and the mechanism that seals the patch to the receptacle thereby necessitating the use of additional apparatus which substantially increases the cost of the final product.